Chapter 8: Transport in Mammals

Syllabus Objectives:

(a) Identify the main blood vessels to and from the heart, lungs, liver and kidney

(b) State the functions of blood

• red blood cells - haemoglobin and oxygen transport

• white blood cells - phagocytosis, antibody formation and tissue

rejection

• platelets - fibrinogen to fibrin, causing clotting

• plasma - transport of blood cells, ions, soluble food substances, hormones, carbon dioxide, urea, vitamins, plasma proteins

(c) List the different ABO blood groups and all possible combinations for the donor and recipient in blood transfusions

(d) Relate the structure of arteries, veins and capillaries to their functions

(e) Describe the transfer of materials between capillaries and tissue fluid

(f) Describe the structure and function of the heart in terms of muscular contraction and the working of valves

(g) Outline the cardiac cycle in terms of what happens during systole and diastole (Histology of the heart muscle, names of nerves and transmitter substances are not required)

(h) Describe coronary heart disease in terms of the occlusion of coronary arteries and list the possible causes, such as diet, stress and smoking, stating the possible preventative measures

8.1 Transport in living organisms

How do useful materials reach all body cells / waste from the cells are removed rapidly?

8.1.1Features of a circulatory system

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Simple Organisms - Simple Diffusion

Body cells are close to their surroundings.

Complex Organisms – Diffusion is NOT effective as cells are far away from body surfaceNeed a transport system Circulatory system in mammals, for example

A circulating fluid to carry materials

A pumping device to drive fluid around body

A system of branched tubes/ vessels connected to the heart through which fluid can circulate and reach all body cells

Made up of

Either by

8.2 Blood

Definition: A fluid tissue Average human adult has about 5.5 litres of blood Composition of blood:

8.2.1 Transport of oxygen (RBC)

Haemoglobin + Oxygen Oxyhaemoglobin

8.2.2 Protective functions of blood (WBC+platelets+some plasma proteins)

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Blood Heart

Plasma Blood cells Platelets

Made up of

Blood

White Blood Cells (WBC)

Red Blood Cells (RBC)

Pale yellow liquid

90% water Carry

dissolved substances Biconcave,

flattened discs No nucleus Contain

haemoglobin Life-span: 3-

4 months Formed in

bone marrow Destroyed in

spleen and liver

Colourless Contains a

nucleus Can move

about and change its shape

Lives for only a few days

Lymphocytes Phagocytes Produced in

lymph glands and lymph nodes

Produced in bone marrow

Cell fragments Formed in

bone marrow

Function: Transport of

dissolved substances

Function: Transport of

Oxygen

Function: Protective Clotting of

blood

Protective Functions Air sac in lung

Body cells(Purplish red) (Bright red)

Phagocytosis Antibody production Clotting of blood

Protective functions

Phagocytes engulf and digest foreign particles (eg. Bacteria that enter blood)

Lymphocytes produce antibodies (proteins)

Platelets + damaged cells

8.2.3 Blood Groups

Surfaces of RBC contains antigens, which are the same in all your RBCs Natural antibodies do not react with the antigens on your RBC

o However, it could react with antigens from another persono When this happens, the antibodies will cause the RBC to clump

together (agglutination) – See Sect 8.2.2 above.o Clumping of RBC leads to the blockage or small blood vessels

prevent smooth flow of blood death Your blood group is based on the types of antigens and antibodies

present in your blood

Blood Group Antigen on RBC Antibody in plasmaA Antigen A Antibody bB Antigen B Antibody a

AB Antigens A and B No antibodiesO No Antigen Antibodies a and b

Note: Whenever Antibody a reacts with antigen A clumping occurs Antibody b reacts with antigen B clumping occurs No antibody reacting with antigen, or vice versa no clumping occurs

Recipient blood group

Antibody in

recipient’s plasma

Donor’s blood groupA (antigen A) B (antigen B) AB

(antigens A & B)

O (no antigens: universal

donor)A b - + + -B a + - + -

AB (universal acceptor)

No antibodie

s

- - - -

O a and b + + + -

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Antibodies cause bacteria

to clump together

(agglutination)

Antibodies kill bacteriaBacteria

clumps undergo

Antitoxins neutralize

toxins produced by

bacteria

Ca2+ + Vit. K + thrombin

Fibrinogen fibrin threads network(Soluble in plasma)

(Insoluble)

+ trapped RBC

Forms blood clot

Legend : + agglutination (clumping happens) (not compatible) - no agglutination (no clumping) (compatible)

8.3 Blood Circulation in humans

Mammals possess a double circulation In double circulation, blood passes through the heart twice before it

completes one circuit of the body

8.3.1 Pulmonary circulation/circuit Carries deoxygenated blood (low oxygen conc) from heart

to lungs at low pressure (flows slowly) Gives blood time to be well oxygenated

Blood then becomes oxygenated (high oxygen conc) Oxygenated blood then returns to the heart (to Left

Atrium)

8.3.2 Systemic circulation/circuit Distributes oxygenated blood from heart to all parts of the

body except the lungs Then returns the deoxygenated blood from these parts to

the heart again

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Median septum

LegendA: AtriumV: Ventricle

Body parts other than lungs

Low-pressure circulation

High-pressure circulation

Blood leaves heart at high pressure so that it can reach all the body tissues at a faster rate, bringing oxygen to them rapidly

8.4 The Heart

A muscular organ Contracts and relaxes regularly throughout life Consists of 4 chambers

2 atria (upper chambers) (LA & RA) 2 ventricles (lower chambers) (LV and RV)

Median septum separates LA & LV from RA & RV Prevents mixing of oxygenated blood on left side of heart with

deoxygenated blood on right side Ensures

All oxygenated blood is sent to all parts of body All deoxygenated blood goes to the lungs

Structure of atria and ventricles Chamber Structure AdaptationAtria Walls are thin Only needs to force blood into ventriclesVentricles

Walls are thick Needs to push blood out of the heart

Walls of LV is thicker than RV enables it to pump blood more forcefully at high pressure to the rest of the body

Presence of valves to prevent backflow of blood ensure that blood flows in one direction only

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Tricuspid valves

Bicuspid valvesSemi lunar valves

Ensures blood flows in one direction

8.4.1 Mode of action of the heart

Ventricle relaxing Ventricle contracting

1 heart-beat = 1 contraction (systole) + 1 relaxation (diastole) of atria & ventricles

As ventricles contract arteries dilate

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Atria relax

Blood fills atria from veins Atria contracts

Tricuspid/Bicuspid valves open

Blood enters relaxed ventricle

Ventricle contracts

Semi lunar valves openBlood pumped into arteries

Tricuspid/Bicuspid valves close “lub” sound

Atria begin to relax

Ventricles relax

Semi lunar valves close “dub” sound

o Each dilation cause elastic walls of arteries to recoil force blood along as a series of waves/pulses

o This pulse rate is High after exertion Low during rest

8.5 Blood vessels

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Arteries Capillaries Veins

Blood vessels

Carry blood away from heart

Take nutrients, oxygen and useful substances to the cells and remove

waste produced in cells

Carry blood towards heart

8.5.1 Comparison between blood vessels

Blood vessel Artery Capillary VeinWall and Lumen Wall is thick,

muscular and elastic

Wall is one-cell thick, lumen size of a RBC

Wall is thin, less muscular and elastic

Diagram of cross-section

Valves Absent Absent Semi-lunar

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valves to prevent backflow of blood

Blood flow 1. Blood moves along by contraction of the muscles of its walls.

2. Blood flows under great pressure, fast, in spurts.

1. Blood flows smoothly

2. Pressure at arteriole end > pressure at venule end.

1. Blood flows smoothly and slowly

2. Blood moves along vein by contractions of the body muscles on the vein

Nature of blood Oxygenated (except for pulmonary artery)

Oxygenated at arteriole end, deoxygenated at venule end (except lungs!)

Deoxygenated (except for pulmonary vein)

8.5.2 Coronary arteries

2 Coronary arteries supply the heart muscles with nutrients and oxygen

Coronary heart disease (CHD)

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Fat deposits (atherosclerosis)

Blood clots (thrombosis)

Partially block the lumen of coronary arteries

Obstruct blood flow to the heart muscles

Heart muscles do not get enough nutrients/oxygen

Heart muscles start to degenerate

Severe heart pain heart attack

Causes of CHD: High fat diet, smoking, being overweight, lack of exercise, stress

8.6 Transfer of materials between capillaries, tissue fluids and body cells

Body cells are bathed in tissue fluido Tissue fluid = dilute plasma without plasma proteins

Role of tissue fluid:o To allow nutrients and oxygen to diffuse out of the blood

in capillaries into the fluid, and then eventually to body cells

o Waste products formed by the cells diffuse out of the tissue fluid, and from there diffuse into the blood in the capillaries

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Some enters tissue fluid